This application is continuation-in-part of, and claims the benefit of, U.S. patent application Ser. No. 10/098,155, filed Mar. 14, 2002, which claims benefit of U.S. Provisional Application No. 60/353,722, filed Feb. 1, 2002, and entitled NUCLEIC ACID MOLECULES ENCODING CEL I ENDONUCLEASE AND METHODS OF USE THEREOF, and which is incorporated herein by reference.